Cardinal Keith O'Brien is facing legal action over a new allegation of abuse dating back to the 1980s.
A former seminarian, who has not been named, told the Herald newspaper he decided to speak out after the recent spate of allegations.
Solicitor Cameron Fyfe confirmed that he has been instructed by the man to make a claim for compensation against Cardinal O'Brien.
Earlier this month, Cardinal O'Brien issued a sweeping apology and admitted his sexual conduct had at times "fallen below the standards expected of me".
The cardinal, who was Britain's most senior Catholic cleric, stepped down from his post as archbishop of St Andrews and Edinburgh a day after three priests and a former priest made allegations of "inappropriate" behaviour against him.
He asked for forgiveness from those he had "offended" and said he would play no part in the public life of the Church in Scotland.
The latest allegation comes from a former priest, who was 19 at the time of the alleged incident. He said the cardinal invited him to his room after dinner.
He told the Herald: "He had been talking about himself, how he was going places, his career had been mapped out and it was for God to decide.
"I can't remember the exact phrase he used but he told me he would always look after me and how good a priest I'd be.
"Until this stage I'd thought how excellent it would be to be a priest in his diocese.
"But that's when it happened. After a few minutes he released me and I was able to make my excuses and go."
The former priest's solicitor Mr Fyfe said he is also exploring the cases of six other clients who allege they were abused by priests.
He said: "I have been instructed to make a claim for compensation against Keith O'Brien and his archdiocese on the basis of abuse my client suffered at the 1980s while at seminary.
"He is a good witness. You get to assess credibility over the years when you've seen so many clients in this situation and he's entirely credible and would be a good witness.
"This is a new allegation, I think originally there were four priests who made allegations against O'Brien, so this is over and above that, and also over and above six clients I have dealt with who are seeking to make claims."
A spokesman for the Catholic Church in Scotland said: "The church is disturbed to hear of these allegations. Any complaints raised will be taken very seriously."